Sorry, I'm in new trouble again. I came to a room full of paintings. Although I can go out, I can also talk to the boy in the painting. But I can't unlock the next scene. The door was locked.
Hi again XD the key you need is on the room full of paintings. You need to check out the wall until you find a key. If you can't find it, try leaving the room (and go back where the mirror is) and enter again.